Ggggggggg

1. Seasons
What do your students think causes the seasons?
Images at http://nix.ksc.nasa.gov/info
Created by the Lunar and Planetary Institute
For Educational Use Only
LPI is not responsible for the ways in which this powerpoint may be used or altered.

2. Let’s Look at Some Data!
• Temperatures around the World
• Daylight hours

3. Average Daily Temperatures (°F) in Tourist Cities
(from http://www.infoplease.com/ipa/A0004587.html ))
January April July October
Cape Town (South Africa) 69 66 60 65
Caracas (Venezuela) 75 81 78 79
London (United Kingdom) 44 56 73 58
Mexico City (Mexico) 66 77 73 70
Montreal (Canada) 22 51 79 56
Moscow (Russia) 21 47 76 46
Nairobi (Kenya) 77 75 69 77
Paris (France) 42 60 76 59
San José (Costa Rica) 75 79 77 77
Seoul (Korea) 33 62 84 67
Singapore 86 89 87 88
Stockholm (Sweden) 31 45 70 48
Sydney (Australia) 79 73 62 72
Tokyo (Japan) 48 64 84 70

4. True color images
June
December
March
September
Images at http://www.nasa.gov/vision/earth/features/blue_marble.html

5. Animation-Earth’s Life through Seasons

6. Daylight Hours Across the Globe
Time is indicated as number of hours (h)
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
10.5 h 11 h 12 h 12.5 h 13 h 14 h 14.5 h 14 h 12.5 h 12.5 h 11 h 11.5 h
14.5 h 13.5 h 13.5 h 12.5 h 11 h 11 h 11 h 11.5 h 11.5 h 12.5 h 14 h 14.5 h
12 h 12 h 12 h 12 h 12 h 12 h 12 h 12 h 12 h 12 h 12 h 12 h
17.5 h 15.5 h 13.5 h 11.5 h 10 h 8.5 h 8.5 h 9.5 h 11.5 h 13 h 15 h 16.5 h
5 h 7 h 10 h 13.5 h 17.5 h 21.5 h 22 h 18 h 15.5 h 11.5 h 8.5 h 5.5 h
12 h 12 h 12 h 12 h 13 h 13 h 12 h 12 h 12 h 12 h 12 h 12 h
15 h 14 h 13.5 h 12.5 h 11.5 h 10 h 10.5 h 11 h 11.5 h 12.5 h 14 h 14 h
9 h 10 h 11 h 13.5 h 15 h 17 h 16.5 h 15.5 h 13.5 h 11.5 h 10.5 h 9.5 h
24 h 24 h 19 h 14.5 h 0 h 0 h 0 h 0 h 7 h 15 h 24 h 24 h
Miami
Brisbane
Nairobi
Punta Arenas
Nome
Singapore
Cape Town
Seattle
Vostok
http://www.lpi.usra.edu/education/skytellers/seasons/activities/light.shtml

7. Let’s Start with some Observations
• Using free downloaded computer program,
Stellarium: http://www.stellarium.org/
– Stellarium is planetarium software that shows exactly what
you see when you look up at the stars. It's easy to use, and
free.
• Let’s look at sunrise & sunset, and Sun’s height in the
sky.

8. Height of Sun for USA
Winter: The Sun rises in the southeast, stays low
in the sky, and sets in the southwest.
Spring: The Sun rises due east, moves higher in
the sky than in winter, and sets due west.
Summer: The Sun rises in the northeast, travels
high (near zenith), and sets in the northwest.
Fall: The Sun rises due east, travels to a
medium-height in the sky, and sets due west.

9. What Causes Earth’s Seasons?
• Earth’s axis is tilted 23.5 degrees – it always points in
the same direction (Polaris, the North Star) as we
orbit our Sun once a year
• This tilt causes the hemispheres to alternate in the
amount of our Sun’s light and heat they receive
through the year
Image at http://www.lpi.usra.edu/education/skytellers/seasons/about.shtml

10. More daylight hours, more direct sunlight
Northern Hemisphere Summer
Image at http://www.lpi.usra.edu/education/skytellers/seasons/about.shtml

11. Earth’s orbit is almost a perfect circle
• Earth is CLOSEST to our Sun (91 million
miles) in winter—January 3
• Earth is farthest from on our Sun (94
million miles) in summer –July 4

12. Seasons on Other Planets
• In some cases, the changing distances from the Sun
will affect the seasons.
• In others, the axial tilt will make a huge difference!
Image at http://photojournal.jpl.nasa.gov/catalog/PIA01589
Image at http://photojournal.jpl.nasa.gov/catalog/PIA02963

13. Seasons on Planets
Planet Axial Tilt Eccent. Orbit Perihelion Aphelion
Mercury 0° 0.21 88 days 28 mill. Miles 43 mill. miles
Venus 177° 0.01 224 days
Earth 23° 0.02 365 days 91 mill. miles 94 mill. miles
Mars 25° 0.09 686 days 129 mill. miles 155 mill. miles
Jupiter 3° 0.05 12 years
Saturn 27° 0.06 30 years
Uranus 98° 0.05 84 years
Neptune 30° 0.01 165 years

14. Mars’ Orbit and Seasons
At summer solstice, Mars is 153
million miles from the Sun
At autumnal equinox, Mars is 134
million miles from the Sun
At winter solstice, Mars is 128
million miles from the Sun
At vernal equinox, Mars is 145
million miles from the Sun
Original images from http://photojournal.jpl.nasa.gov/index.html